The aclonifen effect in action
Reliability matters when controlling grass-weeds at pre-em. Since its introduction 2020, Proclus (aclonifen) has proven its ability to control grass-weeds in different seasons with different establishment conditions.
Apply Proclus in partnership with Liberator (flufenacet + diflufenican) to unleash the potential of three complimentary actives at once. Flufenacet’s site of action is at the roots while, aclonifen and diflufenican remain on the surface to control emerging shoots. Working together, they offer high levels of weed control and adaptability to wetter and drier conditions.
Black-grass and Italian rye-grass can both cause serious problems and require intensive programmes of cultural and chemical controls to protect yield in the crop. Adding more actives in a stack or sequence will improve overall control from the residual herbicide programme.
Trials and field experience suggest mixes of Proclus + Liberator + prosulfocarb, and Alternator / Octavian Met (metribuzin + flufenacet + diflufenican) + Proclus provide excellent weed control at pre-em.
Aclonifen provides protection deep into autumn because it is moderately persistent. As a result it protects against later germinating weeds without necessarily needing a top up spray.
Liberator + Proclus provides all-round pre-emergence control of grass-weeds and broad-leaved weeds in winter wheat when used in accordance with the following application guidelines:
• Must be applied pre-emergence of the crop, ideally within 48 hours of drilling
• Liberator + Proclus should be applied uniformly to a fine, firm seedbed to form a homogenous layer
• Do not disturb the soil after application of Liberator + Proclus as this will affect the efficacy of the products
• Observe drilling depth requirements on both product labels before application (32 mm of settled soil)
• Apply using a horizontal boom sprayer, in 200-400 litres of water per hectare as a MEDIUM spray (BCPC category)
• Use application rate of 0.6 L/ha Liberator + 1.4 L/ha Proclus in wheat and 0.6/ L/ha Liberator + 1 l/ha Prolus in barley.
Ryegrass has consistently been a problem at Littlehales Farm, according to Arable Manager David Pugh. “I’ve been responsible for the arable operation for 13 years. At first, we relied on post-em chemistry, Axial and Pacifica. But about eight years ago it was clear we had resistance. One plant would be yellow and dying, but next to it there would be a completely healthy ryegrass plant.”
David Pugh, Arable Manager, Littlehales Farm, Shropshire
“If I’m honest, at first we mismanaged it a little, carrying on the same way and waiting for the next ‘silver bullet’. But six years ago, we got more serious and started using more cultural controls and stacking effective pre-em chemistry.”
Despite two relatively difficult seasons for weed control, Mr Pugh has managed to stay on top of the problem, keeping weed numbers steady rather than increasing.
A robust pre-em stack is a key part of the weed control programme. “Proclus + Liberator + Defy has been our pre-em for the last few seasons. Proclus is definitely adding to the control, it’s hard to put a number on but you can see it.”
Despite good performance from herbicides, Mr Pugh accepts that the days of the solution coming out of a can are gone. He uses herbicides as management tools alongside cultural techniques and changing cropping.
Littlehales Farm covers 1500 acres with a further 1600 acres contracted, all with predominantly medium soil. The farm mainly grows combinable crops with a small area rented out for root production. Italian ryegrass is the main problem weed, but there are occasional black-grass patches as well.
“We have very little black-grass, I believe that it mainly comes in on balers, if we see any plants, we rogue them immediately. The ryegrass problem isn’t terrible, some fields are rogueable, with a spattering of ryegrass, others have more of a problem but are still manageable. Headlands tend to be the main problem areas.”
When the farm first started to get serious about ryegrass control, Mr Pugh was a little bit frustrated about how much advice there was out there for black-grass but not for ryegrass.
“Most information was for black-grass control, but we needed to focus on ryegrass. Delayed drilling helps but not to the same degree.”
On farm, they typically cultivate after harvest using a Sumo Quatro before spraying off and then drilling with a low disturbance Horsch Serto. They use variable rate to target weed patches, typically the headlands with 20% more seed.
Cleaner fields are drilled first, starting in late September and continues until the second week of October. “By some standards this is not late-drilling, but we don’t want to lose crop competition. Too much bare earth gives weeds the opportunity to cause problems.”
“We move less soil each season, which definitely helps with weed control. But I don’t think that direct drilling would be right for us as things stand. Straw is taken off the farm and swapped for muck, plus we have our own chicken sheds which also provide manure which needs to be incorporated.”
Removing straw rather than chopping and spreading also causes some compaction that needs rectifying. During the process of moving and loading bales, contractors inevitably stray from tramlines.
Hand rogueing and topping also help him to keep on top of weeds. The field margins are topped in spring and before harvest to prevent weed seeds being dragged into the field by the combine and grain carts.
Agronomist Tom Pope advises a number of farms in Dorset and Somerset for Agrovista. Although weed problems are fairly restrained, there are a small number of locations having problems with grass weeds.
“Weed problems tend to affect fields rather than whole farms. I advise a lot of land over chalk which is relatively weed free. Black-grass problems are mainly on heavy Somerset clays, but it seems to be slowly spreading to more farms. Some other farms have minor Italian ryegrass problems, and one has some really nasty stuff.”
“Ryegrass has been a problem on the farm for years. Sometimes it gets a bit better, but it seems to adapt to changes in strategy and get worse again. The whole farm isn’t plagued with ryegrass, but it is spreading. The worst field was resistance tested in 2020 which showed resistance to pendimethalin, flufenacet and most post-em chemistry”
The farm grows wheat, barley, oilseed rape and some winter linseed, rye and maize. Cropping is focused on achieving the best margin but the range of crops mean there are good opportunities for cultural control of weeds too.
“There’s also black-grass in parts of the farm that don’t have ryegrass. Overall, the land is quite varied, some of it is at about sea level and other parts are at 300 feet. There is clay but also lots of flint within the soil which limits cultivation options because it wears out equipment so quickly.”
Crops are established with a strip tillage Claydon drill. Winter cereals generally go in from early to mid-October. Mr Pope points out that it can be quite wet and windy in this area so spray timing and application may be difficult.
“We use robust pre-ems to control weeds in autumn. There are quite a lot of actives available in wheat, so we can get good control, some of the other crops with fewer actives cause more difficulty.”
In wheat, Mr Pope has used Liberator + Proclus + Defy with some good results. Avadex is also used on fields with black-grass problems.
“We first used Proclus against black-grass two years ago, it worked very well, so last autumn it went against ryegrass as well. It worked incredibly well, walking the crops in spring we struggled to find many ryegrass plants even though it was a high-risk field.”
Despite good results from herbicides, cultural controls are also important. Delaying drilling and to a lesser extent spring crops are valuable tools. Ploughing is also an option when things get very bad. “The field with the very bad resistance test results was ploughed to bury the seed, it was then in stubble turnips followed by maize to try to clean it up.”
Peter Waltham, Agrovista Agronomist
Advising farmers in Dorset, Somerset and Wiltshire, Agrovista agronomist Peter Waltham is keen to point out that contrary to received wisdom, black-grass is a serious problem in the West of England.
“The idea that black-grassmainly affects the East is a myth, it’spretty badand the biggest increases are in this part of the country. There’s been a noticeable hit on yield where there is really bad black-grass, and that’s in a season where the harvest has been generally poor with one or two exceptions.”
“We’ve had two years of difficult weed control, there were lots of crops without residuals last autumn and the generally wet weather has made it a really tough year all round.It’s going to be make or break for many this time round because of the build up in the weed population.”
Mr Waltham anticipates many farmers having to put fields to grass or SFI schemes if there is another year with high weed pressure.Unfortunately, delaying drilling is off the menu for many because of the fear of a repeat of last autumn and winter.
“One or two might delay, most will not want to leave it too late and take too much risk. This is a wetter part of the country so delaying drilling is inherently a riskier tactic. I think the main thing is not to go too early, waiting until at least the 20 September and avoid using pre-ems on very dry seedbeds.”
Mr Waltham expects some fairly hefty herbicide programmes this autumn to cope with the weed threat. “Against black-grass, Liberator + Proclus and Avadex is the starting point, against brome I will use pendimethalin instead of the Avadex to avoid needing a second pass.”
“Follow up will be Luxinum + picloinafen or Octavian Met. It’s important not to apply them too close together, if there’s heavy rain it can wash herbicides down to the roots causing crop effects.”
Mr Waltham suggest two weeks is a sensible starting point, but a lot depends on the season. “If you see a good opportunity with the right weather and crops up and looking ok then get in there with a follow up. Remember that you could do a spring Atlantis instead if you have a susceptible population.”
He thinks a lot of work is needed before getting to drilling this year. “Soils have taken a hammering; in many places the top layer has no structure and is lacking microbial activity. Simple advice but get a spade and check where there the problems are and what implement you need to use. Mineralising some nitrogen with cultivation will help things get up and running which is what everyone will want to see this autumn.”
“The surface is drying out, but it should still respond to a light surface cultivation to get a chit of weeds to spray off. Getting at least one good stale seedbed before drilling is important given the level of grass-weeds.”
Jonathan Guy, ProCam agronomist, South Yorkshire.
ProCam agronomist Jonathan Guy advises farms across South Yorkshire. Both black-grass and Italian ryegrass cause problems in his area, but on balance, ryegrass is more troublesome to control.
“A lot of ryegrass seems to be nigh on impossible to control in a cereal crop. Spring cropping is very effective against high black-grass populations but often not for ryegrass. It can still germinate and produce a large infestation in a spring barley crop.”
“Over the last few years, I have had resistance tests done on some difficult to control ryegrass across the county. Most samples came back showing RRR resistance ratings for contact-acting herbicides, and resistance to residual chemistry flufenacet and prosulfocarb too. This meant I had to look at something else to get good pre-em control of ryegrass. Darren Adkins of Bayer suggested using Proclus (aclonifen) in the mix with Liberator (flufenacet + diflufenican) which had given good results on ryegrass in other parts of the country.”
“Autumn 2021 was my first year using Proclus. The results were good and it certainly helped control ryegrass, but seedbed quality is really important in order to get the benefit. The ryegrass has to grow through a layer of aclonifen on the soil surface which means the ground needs to be even, without lots of clods and consolidated for maximum product efficacy.”
“Another thing to watch is heavy rainfall just after application. In general, I would say you have to be more careful than just using Liberator. Proclus is pre-em only, so the sprayer needs to be chasing the roller after the drill so that it is applied at the right time.”
“For grass weeds it is cultural control first and out of the can last. Spring cropping and delayed drilling work for black-grass. To deal with ryegrass, I recommend paying attention to the stale seedbed. Create a stale seedbed as if you were sowing a grass ley, use a roller to consolidate and promote maximum germination before drilling.”
“It all works well in theory, but moisture levels can be a problem. Dry Septembers seem to be quite common, which means you must wait until rain for germination, however once it starts raining in late September / early October, drilling starts and ryegrass ends up emerging with the crop; this is where the advice and the practicality break down. There’s no simple answer. Know what resistance levels you are dealing with, but have a back-up plan, to accommodate whatever the weather throws at you.”
Farming in Shropshire at a relatively exposed site between 150–200m elevation, Andrew Williamson aims to drill in September. “We always try to drill winter wheat by the end of September. From experience, this is the economic optimum with reliable establishment.”
“Last year, we were delayed by wet weather in September, but we managed to drill in the second week of October and apply the pre-em, unfortunately Storm Babet hit not long after with over 50mm of rain falling in one day. You can imagine what that did to crops and the pre-em herbicide.”
Andrew Williamson, Shropshire Grower
Mr Williamson estimates that marketable tonnage of crops will be 50% down on average this year. This is accounted for by poorer yields, a greater proportion of lower yielding spring crops and around 12% of land being put into an SFI scheme rather than redrill in poor conditions.
Using a Horizon direct drill to establish crops, Mr Williamson does very little cultivation, only to incorporate manure and biosolids. The move to direct drilling was to make the farming system more resilient, but last autumn he noticed that neighbours with a plough and combi drill seemed to cope better with the wet weather.
“I still think direct drilling is the right approach but coping with wet autumns is something we need to improve. Drilling spring crops was fine, and the soil structure is resilient and there has been relatively little damage to soil despite fieldwork in wet conditions.”
He points out that without cultivation, the soil surface tends to stay moister. Typically, that would be a benefit for crop establishment and pre-em herbicide performance, but the exceptional quantity of rain last autumn meant it was a drawback.
In cereals, Italian ryegrass is the main problem weed. He uses Liberator + Proclus at pre-em and sometimes follows up in spring with a post-em on high-pressure areas as well as hand rogueing. Until the last two years, weeds have been well under control, but wet and mild winters undoubtedly encourage ryegrass. Nevertheless, he prefers not to use late drilling for control because October drilled crops aren’t reliable at his location.
A wider rotation with a good balance of spring crops is the main cultural weed control method. He uses a six-year rotation containing two wheats, oilseed rape, oats and barley.
“Oilseed rape is now a one year in six crop to culturally manage slugs, flea beetle and disease. Slugs especially seem to be getting worse probably because of the mild winters.”
He is also participating in the Bayer Carbon Project which is looking at how to reduce the carbon footprint of farming, mainly through better management of nitrogen.
“Nitrogen fertiliser is the main input that influences your carbon footprint. It has also been very expensive over the last two years, even though it has come down now it’s still important to use it more efficiently.”
He uses an N sensor to apply fertiliser more accurately and with the project is trialling how to cut rates without a significant yield loss. The trials are testing a cut rate versus the farm standard and a cut rate plus foliar N.
So far, yield losses from cutting the rate are too great, their monetary value far exceeds that of the carbon and input costs saved. But Mr Williamson is keen to keep looking for ways to improve use efficiency of all inputs because costs continue to increase.
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